Sensors and sensor interface systems

ABSTRACT

An apparatus, comprising a housing; a first connector coupled to the housing and having a first plurality of contacts; a second connector coupled to the housing and having a second plurality of contacts; and a circuit electrically connected to at least one of the first contacts and at least one of the second contacts. The circuit is encapsulated within the housing. The circuit is configured to generate an output signal in response to a resistance sensed at the at least one of the first contacts.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional application of U.S. patentapplication Ser. No. 13/754,710 filed on Jan. 30, 2013, which claims thebenefit of U.S. Provisional Patent Application Ser. No. 61/592,803,filed on Jan. 31, 2012, each of which is incorporated herein byreference

BACKGROUND

Embodiments relate to sensor systems and, in particular, interfaces forsensor systems.

Some sensors can use resistivity to indicate sensed information. Forexample, a thermistor can indicate a sensed temperature through itsresistance. A circuit can be used to measure the resistance. A vehiclecan include multiple such sensors, such as temperature sensors forintake air, exhaust, coolant, or the like.

BRIEF DESCRIPTION OF THE DRAWINGS

The description herein makes reference to the accompanying drawingswherein like reference numerals refer to like parts throughout theseveral views, and wherein:

FIG. 1 is a block diagram illustrating a sensor interface moduleaccording to an embodiment.

FIG. 2 is a block diagram illustrating a sensor interface moduleaccording to another embodiment.

FIG. 3 is a block diagram illustrating a buffer of a sensor interfacemodule according to an embodiment.

FIG. 4 is a block diagram illustrating a sensor according to anembodiment.

FIG. 5 is a block diagram illustrating an engine control systemaccording to an embodiment.

FIG. 6 is a graph illustrating a variability in sensed signals without asensor interface.

FIG. 7 is a graph illustrating a variability in sensed signals with asensor interface according to an embodiment.

FIG. 8 is a graph illustrating another variability in sensed signalswithout a sensor interface.

FIG. 9 is a graph illustrating another variability in sensed signalswith a sensor interface according to an embodiment.

FIG. 10 is a block diagram illustrating an engine system including anafter-treatment system according to an embodiment.

DETAILED DESCRIPTION

Embodiments will be described with reference to the drawings. Althoughparticular embodiments will be described, the scope of the followingclaims is not limited to these embodiments. In contrast, alterations,modifications, combinations, or the like can be made.

FIG. 1 is a block diagram illustrating a sensor interface moduleaccording to an embodiment. In an embodiment, the sensor interfacemodule 10 includes a housing 12. The housing 12 can be configured tosubstantially encapsulate a circuit 14. A first connector 16 and asecond connector 18 are coupled to the housing 12. In an embodiment, theconnectors 16 and 18 can be coupled to the housing 12 by wires or otherconductors. In another embodiment, the connectors can include connectorhousings that are integrally formed with the housing 12. In anotherembodiment, the connectors 16 and 18 can include connector housings thatare mechanically attached to the housing 12. The connectors 16 and 18can be coupled to the housing 12 using any combination of suchtechniques or similar techniques.

The connectors 16 and 18 can each include a plurality of contacts. Theconnectors 16 and 18 can have a same or different number of contacts.The circuit is electrically connected to at least one of the contacts ofthe first connector 16 and at least one of the contacts of the secondconnector 18. Connections 20 and 22 represent connections between thecontacts of the connectors 16 and 18 and the circuit 14.

In an embodiment, the circuit 14 can be configured to generate an outputsignal in response to a sensed resistance. The circuit 14 can be coupledto one or more contacts of the first connector 18. Through the firstconnector 18, the circuit 14 can be coupled to a sensor and, inparticular, a resistance based sensor. For example, the first connector18 can include two contacts that are coupled to the sensor. A resistancesensed between the two contacts can be interpreted as a signal from thesensor. The circuit 14 can be configured to generate the output signalbased on the sensed resistance. Although two contacts have beendescribed, any number of contacts can be used to sense the resistance.For example, a single contact can be used with a node common to thecircuit 14 and the sensor. In another example, the sensor can include abridge circuit with multiple associated contacts. The circuit 14 can becoupled to contacts of the first connector 18 to supply a bias voltage,sense an output voltage, or the like.

FIG. 2 is a block diagram illustrating a sensor interface moduleaccording to another embodiment. In an embodiment, multiple connectionscan terminate and/or pass through the housing 12. For example, as willbe described in further detail below, the second connector 38 can becoupled to a control module. Through the connector 38, a powerconnection 34 can be supplied. In addition, a common node, such as aground 46 can be supplied.

Furthermore, one or more connections between the connectors 36 and 38can be made. For example, a particulate matter sensor can include aheater configured to regenerate the sensor. The connections 40 and 44can be pass-through connections for such a heater connection. However,in another embodiment, a common node can be shared among a pass-throughconnection, the sensor, the circuit, a power supply, a combination ofsuch connections, or the like.

In an embodiment, a connection to a sensor includes connections 20 and42. For example, connection 20 can be used for a sensor signal.Connection 42 can be a common node coupled to a common node 46 ofconnector 38. In another embodiment, connection 42 can be another sensornode, for example, of a differential pair. The module 30 can include anysuch connections, common nodes, pass-through connections, or the like.

In an embodiment, the connection 40 can be a direct connection. Forexample, a wire can be directly connected to contacts of the connectors36 and 38. However, the connection 40 can be formed in other ways. Forexample, the connection 40 can include a part of the circuit 32. Theconnectors 36 and 38 can be soldered to a trace on a circuit board ofthe circuit 32.

In an embodiment, a number of contacts of the first connector 36 can bedifferent from a number of contacts. As described above, each of thefirst connector 36 and second connector 38 can include multiplecontacts. However, all of the contacts of the second connector 38 maynot be used in the first connector 36. For example, the first connector36 can have four contacts, two for a sensor input and return, 20 and 42,and two for a heater of the sensor, 40 and 44. The second connector 38can have two contacts for a heater of the sensor, 40 and 44, an outputsignal 22, and power supply connections 34 and 46.

In an embodiment, the connectors 36 and 38 can be opposite genderconnectors. As will be described below, the module 30 can be used in avehicle control system. By using the same connector with oppositegenders, the module 30 can be placed in line with an existing sensorconnection. Power, other signals, other controls, or the like can betransferred to the circuit 32 through the connector 38, a thirdconnector 48, or the like. Accordingly, existing control systems havinga sensor connection that has degraded or has the potential to degradecan be retrofit with the module 30, making the sensing system moretolerant of variations and extending the useful life.

FIG. 3 is a block diagram illustrating a circuit of a sensor interfacemodule according to an embodiment. In this embodiment, a first connector62 can be configured to be coupled to a sensor. For example, the firstconnector 62 can be a connector configured to mate with a correspondingconnector of a sensor. The circuit 60 can include a sensor bias circuit64 associated with a target sensor. For example, the sensor bias circuit64 can include a pull-up resistor to create a resistive divider with aresistive sensor. In another example, the sensor bias circuit 64 caninclude a bridge circuit. Any bias or interface circuit can be used asappropriate to the target sensor.

The circuit 60 can include input conditioning 66. For example, the inputconditioning 66 can include over-voltage protection, reverse voltageprotection, short circuit protection, or the like. In addition, theinput conditioning 66 can include input offset mitigation circuitry.

The circuit 60 can include an amplifier 68. The amplifier 68 can beconfigured to scale, level-shift, limit, perform a combination of suchfunctions, or the like. In an embodiment, the amplifier 68 can include arelatively low impedance output. Thus, for a resistivity based sensor,variability in connectors, wiring, or the like that can add parasiticresistance will likely be higher than the output impedance of theamplifier 68. Such parasitic effects will have a reduced effect on anoutput sensor signal.

In an embodiment, the circuit 60 can include filter 70. For example, thefilter 70 can be a low pass filter; however, in other embodiments, thefilter 70 can be a high-pass, band-pass, all-pass, notch filter, or thelike according to the sensed signal and/or desired characteristics ofthe signal.

Although illustrated as discrete blocks with individual connections, thefunction of the various circuitry of the circuit 60 could be combined,distributed, or the like. For example, the sensor bias 64, inputconditioning 66, amplifier 68, and filter 70 can be combined togetherinto an aggregate amplifier circuit.

FIG. 4 is a block diagram illustrating a sensor according to anembodiment. In this embodiment, a sensor 90 is disposed with a sensorelement 94 in fluid communication with a channel 98. For example, thechannel 98 can be part of an exhaust system of a vehicle. The sensorelement 94 can include a resistivity based particulate matter sensor.The sensor element 94 can be disposed at least in part in a housing 92.

A circuit 100 can be disposed in a second housing 102. In particular,the circuit 100 can be substantially encapsulated in the second housing102. A connector 104 can be coupled to the second housing 102. Theconnector 104 can be coupled to the second housing 102 similar toconnector/housing couplings described above. For example, the secondhousing 102 can be a separate housing or part of a housing of theconnector 104. A conductor 96 is coupled to the housings 92 and 102. Thecircuit 102 is electrically connected to the sensor element 94 throughthe conductor 96.

The conductor 96 can be coupled to the housings 92 and/or 102 in avariety of ways. For example, the conductor 96 can be coupled to ahousing 92 and/or 102 through a strain relief such as a resin, a clamp,a boot, a strap, or the like. In an embodiment, no connectors arepresent between the sensor element 94 and the circuit 100.

The circuit 100 can be configured to generate an output signal based onthe sensor element 94 in response to a signal received through theconductor 96. For example, as described above, the sensor element 94 canbe a resistive sensor element. The circuit 100 can be configured tosense a resistance of the sensor element 94 and generate an outputsignal accordingly.

Although one conductor 96 has been described, any number of conductorscan be used as desired. Any input or output associated with the sensorelement 94, associated components, or the like can include associatedconductors. For example, as described above, two conductors can beassociated with a heater for the sensor element 94 and two conductorscan be associated with the sensor element 94 itself. In another example,any connection through a first connector 16, 36, or the like describedabove can be routed from the first housing 92 to the second housing 102without intervening connectors.

In an embodiment, the sensor 90 can be used to retrofit existinginstalled sensors. For example, the connector 104 can be configured tohave substantially the same configuration as a sensor to be replaced. Ifadditional connections, such as a connector for power and or othersignals is desired, a connector similar to connector 48 described abovecan be used.

Although a particulate matter sensor has been used as an example, othertypes of sensors can be used with the circuit 100. Any sensor with arelatively high resistivity can be used with the circuit 100. Forexample, the sensor can include a pressure sensor configured to sense apressure due to small resistance changes in material with a relativelylarge quiescent magnitude. In another example, the sensor can include athermistor with a relatively high resistance for an expected temperaturein operation.

FIG. 5 is a block diagram illustrating an engine control systemaccording to an embodiment. In this embodiment, the control system 120includes a sensor 124 having a cable 126 and a connector 128. The sensoris disposed in fluid communication with channel 122. As described above,the channel 122 can be an exhaust system of the engine 150 and thesensor 124 can be a particulate matter sensor.

A sensor interface module 130 can include connectors 132 and 134. Themodule 130 can be coupled to the sensor 124 through the connectors 128and 132. In a particular embodiment, the connectors 128 and 132 can bedirectly connected. Thus, only a single connector pair is disposedbetween the sensor element 125 and a circuit of the module 130.

The module 130 is coupled to a control module 148 through wiring harness140. The harness 140 can include multiple connectors. Connectors 136 and138 are illustrated with examples of optional intervening connectors 144and 142 illustrated in phantom. Any number of connector pairs can bepresent between the module 130 and control module 148. The controlmodule 148 includes a connector 146 coupled to the connector 138 of thewiring harness 140.

The control module 148 can be coupled to an engine 150. For example, thecontrol module 148 can be part of an engine management system. Controlsignals to and from the module 130 and/or other components can beprocessed by the control module 148. The control module 148 can be anyvariety of devices. For example, the control module 148 can be adedicated controller configured to solely interact with the sensor 124.The control module 148 can have a communication interface such as a CANbus interface to communicate with other control systems. In anotherexample, the control module 148 can be an emission control computer of avehicle. In another example, the control module 148 can be a controllerfor the entire vehicle including other non-emission related subsystems.

The module 130 can include a circuit, such as the circuit 14, 32, 60, orthe like as described above. Accordingly, an effect of interveningconnectors of the wiring harness 140 can have a reduced effect on aquality of the signal from the sensor 124.

In an embodiment, the module 130 can be configured to output a signalcapable of driving an input of the control module 148 that is configuredto expect an input from the sensor 124. For example, the control module148 can have bias circuitry for biasing the sensor 124 if the module 130was not installed. The module 130 can be configured to drive such aninput. That is, even if a control module 148 is configured to bedirectly electrically coupled to a sensor 124, the module 130 canaccommodate any such circuitry on the input of the control module 148and/or emulate the sensor 124.

In another embodiment, the control module 148 can have reduced circuitryfor processing an input from the sensor 124. For example, the module 130can include a lower output impedance circuit. Accordingly, requirementsfor input offset currents and voltages associated with the controlmodule 148 can be loosened. That is, the control module 148 can bedesigned with a greater variability and/or magnitude of input offsetcurrents and voltages. For example, cost constraints, materials, and/orother design and manufacturing decisions can result in a control module148 that has input characteristics that can make a connection to a highresistivity sensor difficult if not inoperable. The module 130 can allowsuch lower cost designs to be operable by increasing tolerance of suchinput offset effects.

In an embodiment, the output of the module 130 can be a signal that issimilar to a signal output by the sensor 124. For example, a signal fromthe sensor 124 can be an analog signal. Similarly, the module 130 can beconfigured to output a corresponding analog signal. That is, the signalthat is transmitted to the control module 148 can be an analog signal.In a particular embodiment, the signal is not digitized, packetized, orotherwise digitally processed; however, such functions, transformations,or the like can occur in the control module 148 or other similarcircuitry.

As described above, the channel 122 can be part of an exhaust system.Accordingly, the sensor 124 can be exposed to relatively high heat. Somecircuitry may not operate under such conditions. By placing the module130 offset from the sensor 124 due to the cable 126, a reliability ofthe system 120 can be improved.

FIG. 6 is a graph illustrating a variability in sensed signals without asensor interface. Graph 170 illustrates a variability of output signalsfor two systems due to variability in components, operating conditions,and the like. Axis 178 represents a frequency of occurrence and axis 179is an output level. Curve 172 represents a variability with idealinterconnects between a sensor and a controller, such as the sensor 124and control module 148 of FIG. 5, but without the module 130.

In a particular example, a resistivity based sensor can have asubstantially open circuit when no material is sensed. To distinguishbetween a clean sensor and a disconnected sensor, a resistor can beplaced in parallel with the sensor. Thus, even when the sensor is asubstantially open circuit, the resistance of the parallel resistor canbe sensed. Curve 172 represents such a configuration with variability inthe parallel resistor, components, or the like with idealinterconnections.

Curve 174 represents a variability considering the effect ofinterconnections between the sensor and a controller yet disconnectedfrom a sensor. In an embodiment, connectors of wire harnesses can addparallel resistances. When a sufficient number of such parallelresistances are combined, the effective resistance can approach that ofthe intentionally added parallel resistance. Curve 174 represents suchparasitic effects but with the sensor disconnected.

As illustrated curve 172 overlaps curve 174 in region 176. That is, aconnected sensor cannot be distinguished from an unconnected sensor overthe variability of components and conditions.

For example, a number of connector pairs can connect the sensor to thecontrol module. Assuming that a connector can introduce a 100 MΩresistance between terminals, with four connector pairs, eight 100 MΩparasitic resistances are connected in parallel, resulting inapproximately 12.5 MΩ parallel resistance. Such a resistance could bepresent even if the sensor is not connected.

A 10 MΩ open circuit detection resistor can be used. Accordingly, theparallel parasitic resistance can mask the intended parallel resistance.That is, as illustrated in FIG. 6, a variability of the parallelresistance can overlap with the parasitic parallel resistance. In thisexample, the minimum parallel parasitic resistance in normal operationscan be represented by a lower end of the curve 174. Although the opencircuit detection resistor can have a nominal value of 10 MΩ, theresistance could vary over particular operating conditions and componentvariability to be greater than 12.5 MΩ. To increase the lower limit ofthe parallel parasitic resistance, a number of connections can bereduced; however, this can place an upper limit on connections for asensor.

FIG. 7 is a graph illustrating a variability in sensed signals with asensor interface according to an embodiment. Similar to FIG. 6, graph180 illustrates the variably with axis 188 representing occurrence andaxis 189 representing the output level. In this example, a module suchas the module 130 described above is used. Curve 182 represents thesensor with a parallel resistivity. Curve 184 represents a disconnectedsensor.

In particular, a gap 186 is introduced. A threshold can be establishedto decide whether the sensed value indicates a connected or disconnectedsensor. Since less parasitic components are disposed between a sensorand module, an effect on the output of the module by the parasiticcomponents is reduced. Furthermore, the lower impedance output of amodule can reduce an effect of subsequent parasitic components.

In an embodiment, the module 130 can aid in diagnosing problems in asensor system. For example, a megaohm meter may be needed to measure thesensor resistance if it is directly. In addition the sensor wiring mayneed to be checked to determine if a particular resistance measurementis due to deteriorated wiring. With the module 130 or similar modules, ameasurement can be made at the output of the module 130 reducing a needfor a megaohm meter and the parasitic resistance of sensor wiring neednot be measured as the output of the module 130 can tolerate parasiticresistances that may require a megaohm meter to diagnose.

FIG. 8 is a graph illustrating another variability in sensed signalswithout a sensor interface. Graph 190 again represents an occurrenceaxis 198 versus an output axis 199. Curve 192 represents a systemwithout a module, and an example of variability considering worst caseconditions. Curve 194 represents an example considering idealconditions. Note that in this case, the sensor is connected for bothcurves. Total width 196 corresponds to a potential variability in theoutput from ideal to worst case conditions.

FIG. 9 is a graph illustrating another variability in sensed signalswith a sensor interface according to an embodiment. Graph 200 againrepresents an occurrence axis 208 versus an output level axis 209. Curve202 represents an example of worst case conditions while curve 204represents an example of ideal conditions. However, in contrast to FIG.8, a module as described above is present. Accordingly, not only is avariability within ideal conditions reduced, but a variability betweenworst case and ideal conditions is reduced.

FIG. 10 is a block diagram illustrating an engine system including anafter-treatment system according to an embodiment. In this embodiment,the engine system 220 includes an engine 222 coupled to a particulatematter filter 226 through an exhaust channel 224. The particulate matterfilter 226 can be coupled to a catalyst system 230 through channel 228.For example, the catalyst system 230 can include a diesel exhaust fluidsystem and a selective catalyst reduction system. However, other typesof catalyst systems can be used.

A sensor 248 is disposed in channel 228. The sensor 248 is coupled to asensor interface 234 through cable 246 and connectors 242 and 244. Theconnection between the sensor 248 and sensor interface 234 can be asdescribed above. Thus, the sensor signal 236 can be provided to thecontrol module 238 and be in control of the engine 240. Accordingly, thereliability of the system 220 can be improved.

Although the sensor 248 is illustrated as coupled to channel 228, thesensor 248 can be coupled to other locations upstream or downstream ofthe particulate matter filter 226. For example, the sensor 248 could becoupled to channel 232 downstream of the catalyst system 230, or otherdownstream component. In another example, the sensor 248 could becoupled to the channel 224, upstream of the particulate matter filter226. Moreover, multiple such sensors 248 can be present in the system invarious locations, each with a corresponding circuit as described above.

While embodiments have been described with reference to the drawings,the sprit and scope of the following claims is not limited to thedisclosed embodiments, but on the contrary, is intended to cover variousmodifications, combinations, and equivalent arrangements. In reading theclaims it is intended that when words such as “a,” “an,” “at least one”and “at least a portion” are used, there is no intention to limit theclaim to only one item unless specifically stated to the contrary in theclaim. Further, when the language “at least a portion” and/or “aportion” is used the item may include a portion and/or the entire itemunless specifically stated to the contrary.

1-6. (canceled)
 7. A sensor, comprising: a first housing; a sensorelement disposed in the first housing; a second housing; a conductorcoupled to the first housing and the second housing; a connector coupledto the second housing, the connector including a contact; a bufferelectrically connected to the sensor element through the conductor;wherein: the second housing encapsulates the buffer; and the buffer iselectrically connected to the contact of the connector.
 8. The sensor ofclaim 7, wherein at least part of the connector is part of the secondhousing.
 9. The sensor of claim 7, wherein the conductor is coupled tothe second housing by a strain relief.
 10. The sensor of claim 7,wherein the buffer is configured to generate an output signal inresponse to a resistance of the sensor element. 11-14. (canceled) 15.The sensor of claim 7, wherein the sensor element is a resistive sensorelement.
 16. The sensor of claim 7, wherein the buffer is a circuit thatincludes an input conditioning.
 17. The sensor of claim 16, wherein thecircuit includes an amplifier.
 18. The sensor of claim 17, wherein thecircuit includes a filter.
 19. The sensor of claim 7, wherein the sensorelement is a particulate matter sensor element.
 20. A sensor,comprising: a first housing; a resistive sensor element disposed in thefirst housing; a second housing; a circuit encapsulated in the secondhousing; a conductor coupled to the first housing and the secondhousing, wherein the conductor electrically connects the circuit to theresistive sensor element; and a connector coupled to the second housing,wherein the connector includes a contact that is electrically connectedto the circuit
 21. The sensor of claim 20, wherein at least part of theconnector is part of the second housing.
 22. The sensor of claim 20,wherein the conductor is coupled to the first housing by a strainrelief.
 23. The sensor of claim 20, wherein the conductor is coupled tothe second housing by a strain relief.
 24. The sensor of claim 20,wherein the buffer is configured to generate an output signal inresponse to a resistance of the sensor element.